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Anatomical Adaptations of Boerhavia L. and Commicarpus Standl. (Nyctaginaceae) for Survival in Arid Environments of Namibia

Madeleen Struwig Anine Jordaan Stefan Siebert
Acta Biologica Cracoviensia s. Botanica | 2011 | vol. 53 | No 2 | DOI: 10.2478/v10182-011-0025-0
Keywords Adaptations arid environment avoiders Boerhavia Commicarpus Namibia xerophytes
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Abstract

Members of the Nyctaginaceae Jussieu. are distributed throughout southern Africa. Eight species of the family occur naturally in arid parts of Namibia. These species have acquired the ability to survive and reproduce in these dry conditions. They are xerophytes, which have been described as drought evaders, avoiders, and drought-tolerant. In the Nyctaginaceae, Boerhavia deserticola, B. hereroensis, Commicarpus helenae and C. squarrosus are thought to be drought avoiders. In this study we investigated their stem, leaf and anthocarp anatomy for adaptations to arid environments. The results indicated that the four species are avoiders, with modifications of the trichomes, secretions, crystals, secondary growth, Kranz mesophyll, water storage cells, tannins, mucilage, inner and outer stomatal ledges, large-diameter xylem vessels, and the presence of sclerenchyma in their stems, leaves and anthocarps. These adaptations enable the plants to tolerate arid conditions, conserve water and maintain a high photosynthetic rate, and aid seed dispersal.

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Authors and Affiliations

Madeleen Struwig
Anine Jordaan
Stefan Siebert

Motion planning of planar and redundant underwater serial link manipulator based on minimization of energy consumption

Virendra Kumar Soumen Sen Shibendu Shekhar Roy
Archive of Mechanical Engineering | 2021 | vol. 68 | No 4 | 415-434 | DOI: 10.24425/ame.2021.139312
Keywords underwater manipulator drag added inertia motion planning recursive Lagrangian formulation redundant manipulator obstacle avoidance singularity avoidance
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Abstract

The article describes motion planning of an underwater redundant manipulator with revolute joints moving in a plane under gravity and in the presence of obstacles. The proposed motion planning algorithm is based on minimization of the total energy in overcoming the hydrodynamic as well as dynamic forces acting on the manipulator while moving underwater and at the same time, avoiding both singularities and obstacle. The obstacle is considered as a point object. A recursive Lagrangian dynamics algorithm is formulated for the planar geometry to evaluate joint torques during the motion of serial link redundant manipulator fully submerged underwater. In turn the energy consumed in following a task trajectory is computed. The presence of redundancy in joint space of the manipulator facilitates selecting the optimal sequence of configurations as well as the required joint motion rates with minimum energy consumed among all possible configurations and rates. The effectiveness of the proposed motion planning algorithm is shown by applying it on a 3 degrees-of-freedom planar redundant manipulator fully submerged underwater and avoiding a point obstacle. The results establish that energy spent against overcoming loading resulted from hydrodynamic interactions majorly decides the optimal trajectory to follow in accomplishing an underwater task.
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Bibliography

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[17] A.K. Sharma and S.K. Saha. Simplified drag modeling for the dynamics of an underwater manipulator. IEEE Journal of Ocean Engineering, 46(1):40–55, 2021. doi: 10.1109/JOE.2019.2948412.
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Authors and Affiliations

Virendra Kumar
1
ORCID: ORCID
Soumen Sen
1
Shibendu Shekhar Roy
2
  1. Robotics and Automation Division, CSIR-Central Mechanical Engineering Research Institute, Durgapur, India
  2. Mechanical Engineering Department, National Institute of Technology, Durgapur, India

Obstacle avoidance method of autonomous vehicle based on fusion improved A*APF algorithm

Yubin Qian Hongtao Sun Song Feng
Bulletin of the Polish Academy of Sciences Technical Sciences | 2023 | 71 | 2 | e144624 | DOI: 10.24425/bpasts.2023.144624
Keywords obstacle avoidance path planning fuzzy control tracking control
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Abstract

This paper proposes an autonomous obstacle avoidance method combining improved A-star (A*) and improved artificial potential field (APF) to solve the planning and tracking problems of autonomous vehicles in a road environment. The A*APF algorithm to perform path planning tasks, and based on the longitudinal braking distance model, a dynamically changing obstacle influence range is designed. When there is no obstacle affecting the controlled vehicle, the improved A* algorithm with angle constraint combined with steering cost can quickly generate the optimal route and reduce turning points. If the controlled vehicle enters the influence domain of obstacle, the improved artificial potential field algorithm will generate lane changing paths and optimize the local optimal locations based on simulated annealing. Pondering the influence of surrounding participants, the four-mode obstacle avoidance process is established, and the corresponding safe distance condition is analyzed. A particular index is introduced to comprehensively evaluate speed, risk warning, and safe distance factors, so the proposed method is designed based on the fuzzy control theory. In the tracking task, a model predictive controller in the light of the kinematics model is devised to make the longitudinal and lateral process of lane changing meet comfort requirements, generating a feasible autonomous lane-change path. Finally, the simulation was performed in the Matlab/Simulink and Carsim combined environment. The proposed fusion path generation algorithm can overcome the shortcomings of the traditional single method and better adapt to the dynamic environment. The feasibility of the obstacle avoidance algorithm is verified in the three-lane simulation scenario to meet safety and comfort requirements.
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Authors and Affiliations

Yubin Qian
1
ORCID: ORCID
Hongtao Sun
1
ORCID: ORCID
Song Feng
1
ORCID: ORCID
  1. School of Mechanical and Automotive Engineering, Shanghai University of Engineering Science, Shanghai, China

Social assistance or agency? Attachment Styles Moderate the Impact of Control Threat on Social Relationship Preferences

Agata Gasiorowska Tomasz Zaleskiewicz
Polish Psychological Bulletin | 2023 | vol. 54 | No 4 | 309-317 | DOI: 10.24425/ppb.2023.148849
Keywords social relations agency control threat attachment anxiety attachment avoidance
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Abstract

Building upon Gasiorowska and Zaleskiewicz's (2021, 2023), we explored how a control threat and attachment style influence social relationship preferences. This experiment aimed to investigate how experiencing a control threat affects individuals with secure, anxious, and avoidant attachment patterns when they can choose between seeking assistance from the market, asking a close person for help, or coping with the situation alone. Participants with different attachment styles were randomly assigned to either the lack of control condition ( n = 290) or the having control condition ( n = 277). Individuals with an anxious attachment were more inclined to choose the market-exchange option and less likely to select the agentic and communal options when faced with a control threat. Meanwhile, those with an avoidant attachment exhibited a higher tendency to choose the agentic option, while their preference for noncontingent help decreased after exposure to the control threat. Surprisingly, secure attachment individuals showed an increased preference for noncontingent help and decreased preferences for market exchange and self-reliance when exposed to the control threat compared to when they had control. These findings suggest that participation in market relationships may meet vital psychological needs and serve as a safeguard against attachment insecurities.
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Authors and Affiliations

Agata Gasiorowska
1
ORCID: ORCID
Tomasz Zaleskiewicz
1
ORCID: ORCID
  1. SWPS University SWPS University, Wrocław, Poland

Energy-efficient walking over irregular terrain: a case of hexapod robot

Mindaugas Luneckas Tomas Luneckas Dainius Udris Darius Plonis Rytis Maskeliunas Robertas Damasevicius
Metrology and Measurement Systems | 2019 | vol. 26 | No 4 | 645-660 | DOI: 10.24425/mms.2019.130562
Keywords hexapod walking robot irregular terrain obstacle avoidance energy consumption leg trajectory optimization
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Abstract

Adaptive locomotion over difficult or irregular terrain is considered as a superiority feature of walking robots over wheeled or tracked machines. However, safe foot positioning, body posture and stability, correct leg trajectory, and efficient path planning are a necessity for legged robots to overcome a variety of possible terrains and obstacles.Without these properties, anywalking machine becomes useless. Energy consumption is one of the major problems for robots with a large number of Degrees of Freedom (DoF). When considering a path plan ormovement parameters such as speed, step length or step height, it is important to choose the most suitable variables to sustain long battery life and to reach the objective or complete the task successfully.We change the settings of a hexapod robot leg trajectory for overcoming small terrain irregularities by optimizing consumed energy and leg trajectory during each leg transfer. The trajectory settings are implemented as a part of hexapod robot simulation model and tested through series of experiments with various terrains of differing complexity and obstacles of various sizes. Our results show that the proposed energy-efficient trajectory transformation is an effective method for minimizing energy consumption and improving overall performance of a walking robot.

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Authors and Affiliations

Mindaugas Luneckas
Tomas Luneckas
Dainius Udris
Darius Plonis
Rytis Maskeliunas
Robertas Damasevicius

The obstacle vector field (OVF) method for collision-free trajectory planning of free-floating space manipulator

Tomasz Rybus
Bulletin of the Polish Academy of Sciences Technical Sciences | 2022 | 70 | 2 | e140691 | DOI: 10.24425/bpasts.2022.140691
Keywords space robotics obstacle avoidance obstacle vector field free-floating system on-orbit servicing
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Abstract

Manipulators mounted on small satellites will be used to perform on-orbit servicing, removal of space debris, and assembly of large orbital structures. During such operations, the manipulator must avoid collisions with the target object or the elements of the assembled structure. Planning of the manipulator trajectory is one of the major challenges for the proposed missions because the motion of the manipulator influences the position and orientation of the satellite. Thus, the dynamic equations of motion must be used during trajectory planning. Methods developed for fixed-base manipulators working on Earth cannot be directly applied. In this paper, we propose a new obstacle vector field (OVF) method for collision-free trajectory planning of a manipulator mounted on a free-floating satellite. The OVF method is based on a vector field that surrounds the obstacles and generates virtual forces that drive the manipulator around the obstacles. The OVF method is compared with the classical artificial potential field (APF) method and the rapidly exploring random trees (RRT) method. In the presented examples the trajectory planning problem is solved for a planar case in which the satellite is equipped with a 2 DoF manipulator. It is shown that the OVF method is more efficient than the APF method, i.e., it allows us to solve the trajectory planning problem in some of the cases, in which the APF method is unsuccessful. The time required to find the solution with the use of the OVF method is shorter than the time needed by the APF and the RRT method.
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Authors and Affiliations

Tomasz Rybus
1
ORCID: ORCID
  1. Centrum Badań Kosmicznych Polskiej Akademii Nauk (CBK PAN), ul. Bartycka 18A, 00-716 Warsaw, Poland

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